Dropping Redo Log Group or Member

Dropping Redo Log Group:

To increase or decrease the size of online redo log groups you add or drop online redo log groups. To drop a redo log you must have the alter database system privilege.Use the alter database drop logfile group you can drop the redo log group.

Alter database drop logfile group 3;

But before drop a redo log group follow the following restrictions:

An insatnce requires at least two groups.
You cannot be dropped active or current group means a group can drop only if it is inactive.
Make sure a redo log group is archived.Whan an online redo log group is dropped the system files are not deleted.

Dropping Redo Log Member:

If you want to drop any invalid online redo log member you can drop member by using alter database drop logfile member command:

Alter Database drop logfile member'/opt/luck/redo03.log';

When a redo log member is dropped from the database, the operating system file is not deleted from disk. The control files of the database are updated to drop the member from the database structure. But brfore drop a redo log member you have to follow the following restrictions:

If you want to drop a redo log member and that member is the last valid member of the group, you cannot drop that member.
If the group is current, you must force a log file switch before you can drop the member.
If the database is running in ARCHIVELOG mode and the log file group to which the member belongs is not archived, then the member cannot be dropped.
When an online redo log member is dropped, the operating system file is not deleted.